Heat oil on the Saute function and add the beef, browning on all sides. Once the beef is browned on all sides, turn off the Saute function.
Add onion and pepperoncini to the pot.
In a separate bowl, stir together broth, brine, seasoning, and salt. Pour over the beef into the pot.
Seal lid and set the Pot for 50 minutes on the Manual function. When cycle is complete, allow natural release for 10-15 minutes.
Shred the beef.